Add events detailed page

[Panos512]

Issues with add event:

• [x] Parent's shouldn't be able to post events.
• [x] Provider id is not saved in the db.
• [x] Only first date is saved in the database while the post contains multiple dates on the dates field.
• [x] Only the first even submition works. After that there is an 500 error returned instead.

error:

could not execute statement; SQL [n/a]; constraint [uk5ky4frjmcobbiayt5jyx53mff]; 
nested exception is org.hibernate.exception.ConstraintViolationException: 
could not execute statement

and on the backend:

Hibernate: insert into categories (category) values (?)
2017-06-17 19:40:51.296  WARN 31929 --- [nio-8080-exec-1] o.h.engine.jdbc.spi.SqlExceptionHelper   : SQL Error: 0, SQLState: 23505
2017-06-17 19:40:51.297 ERROR 31929 --- [nio-8080-exec-1] o.h.engine.jdbc.spi.SqlExceptionHelper   : ERROR: duplicate key value violates unique constraint "uk5ky4frjmcobbiayt5jyx53mff"
  Detail: Key (category)=(team) already exists.
2017-06-17 19:40:51.329 ERROR 31929 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [uk5ky4frjmcobbiayt5jyx53mff]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement] with root cause